OS OpenSpace enables web-savvy users to build mash-ups with a range of Ordnance Survey data in line with government aims to make public sector information more accessible.

Under an application programming interface (API) developers will register for a feed of data to experiment with non-commercially. It includes a range of mapping scales covering the whole of Great Britain down to street level.

But before you hang out all the bunting, it's only for some just now:

This week's stage involves a hands-on preview to a dedicated group of developers who will have exclusive access to test functionality and build applications ahead of a public launch early in the new year.

Still, Steve Coast of OpenStreetMap is enthusiastic, at least in the release: "This represents one of the most significant releases of a mapping data API. It will be interesting to see what web developers do with it," he's quoted as saying.

Ed Parsons, who as chief technology officer at OS (before leaving last year for Google) was key in making this happen, remarks on his own blog:

I'd love to see comments from anyone who is part of the alpha, but I guess they are under pretty strict NDA at the moment. One observation is the limit on the number of maps tiles which may be rendered for an API key, this is not something I have seen elsewhere, but I can understand it as a defence against accusations from commercial users of the data of unfairness.

Still is great to see something I put so much effort into during my time at the OS finally reaching the public.

I saw it demonstrated by Ed and his team when I visited OS in 2006; I thought it looked impressive then. Legal wranglings over licences are thought to have held it back.

The point of the Free Our Data campaign (in case it's new to you) is that we argue that data like the OS maps should be available for free commercial reuse (at present it's charged-for, and can be very expensive), and the cost of providing their services funded directly out of taxes. Then, commercial companies could thrive and compete without the drag of the data cost. (As an example, consider the multiplier effect of GPS - which I wrote about here.)